Lubrication of rotating parts such as gears and bearings in gearboxes for wind turbines during operation of the wind turbine is very important. No or not sufficient provision of lubricant to these parts can lead to damages and to failure of such parts. Especially bearings supporting gears and shafts in the gearbox, and more particularly plain bearings, are very sensitive to good lubrication and need at all times sufficiently be provided with lubricant in order not to fail.
During normal operation, in known wind turbine and gearbox designs, lubricant is continuously fed to the rotating parts by means of an electrical pump and usually this is sufficient for feeding the right amount of lubricant to the rotating parts. However, in case of emergency situations like, for example, grid loss or failure of the electrical pump, the lubricant feeding may not be sufficient anymore for the rotating parts in the gearbox, and especially the bearings, to continue working properly.